My spouse has a host of health issues, including vision. We went to see a specialist once and I wasn't understanding what he meant when he referred to something in her eye as "jelly." So I asked him to explain. I finally gave up after about the fifth or sixth time he attempted with increasingly obvious irritation to explain using some variation of the same "it's the jelly" phrase - completely not getting that he needed to explain what "the jelly" was.
Sometimes it's not you, but them.